Cystic echinococcosis is a zoonotic disease of difficult diagnosis and treatment. The use of protoscolicidal agents in procedures is of utmost importance for treatment success. This study was aimed at analysing the in vitro and ex vivo activity of Melaleuca alternifolia oil (tea tree oil – TTO), its nanoemulsion formulation (NE-TTO) and its major component (terpinen-4-ol) against Echinococcus ortleppi protoscoleces obtained from cattle. Concentrations of 2·5, 5 and 10 mg mL−1 of TTO, 10 mg mL−1 of NE-TTO and 1, 1·5 and 2 mg mL−1 of terpinen-4-ol were evaluated in vitro against protoscoleces at 5, 10, 15 and 30 min. TTO was also injected directly into hydatid cysts (ex vivo analysis, n = 20) and the viability of protoscoleces was evaluated at 5, 15 and 30 min. The results indicated protoscolicidal effect at all tested formulations and concentrations. Terpinen-4-ol (2 mg mL−1) activity was superior when compared with the highest concentration of TTO. NE-TTO reached a gradual protoscolicidal effect. TTO at 20 mg mL−1 showed 90% protoscolicidal action in hydatid cysts at 5 min. The results showed that TTO affects the viability of E. ortleppi protoscoleces, suggesting a new protoscolicidal option to the treatment of cystic equinococcosis.